In the land of Fronaldo, the Republic of Biscotti has been aggressively attacked by the Lion Kingdom of Galette. Facing potential defeat, Princess Millhiore summons a hero who can save the country. What she gets is Izumi Shinku, a middle-school boy from Japan. Awaiting him in Fronaldo is the task of becoming hero enough to defeat his enemies while learning the peculiar rules of battle in this strange new world.

Season 2, start off three months after his adventure in Flonyard, Shinku gets summoned back once again, this time bringing Rebecca with him. His cousin and rival athlete Nanami, also is summoned to Flonyard as Galette's Hero. The First Princess of the Principality of Pastillage, Couver, leads her squirrel-like faction into the battlefield as well with the intention of scouting Rebecca to become their hero.